Chassis dynamometers for use in testing vehicles are well known in the art. Such dynamometers are particularly useful for emissions testing of motor vehicles to dynamically load the vehicle engine through the vehicle drive train. Emission testing dynamometer systems attempt to simulated road load forces and vehicle inertia forces that would normally act on a vehicle. Typically, dynamometers have at least one large flywheel attached to the dynamometer's rollers to simulate inertia of the vehicle. Since vehicle inertia is a function of the vehicle weight, a flywheel can not accurately simulate vehicle inertia where the dynamometer is used for several different types and weights of vehicles. Also, the flywheel is a fixed inertia device that can not simulate speed dependant variable load forces that result from windage and friction.
Electronically controlled dynamometer systems have been proposed that attempt to simulate vehicle inertia and road loads. These known systems have not, however, provided a real time inertia simulation in a manner that anticipates loading requirements so that loads are applied simultaneously with changes in vehicle speed. Typically, electronically controlled dynamometer systems apply a load only in response to a measured vehicle parameter such as vehicle speed. Therefore, the load is applied late thereby loading the vehicle engine after the engine has accelerated the vehicle wheels.